Dual-mode surface-mount cavity resonator and filter

A dual-mode surface-mount cavity resonator is proposed. The resonator consists of two identical three-dimensional parts, and planar circuit board. The cavity resonator can be mass-produced by molding techniques and subsequently soldered onto the board. The resonator shows reduced quality factor if compared to conventional air-filled cavities, but in a multi-resonator filter arrangement, cost is greatly reduced because all resonators have identical shape. A dual-mode resonator with an inner volume 11.2 cm³ was designed and built to be resonant at about 2.1 GHz. The unloaded quality factor of a silver-plated resonator is 1400. The two-pole passband shows an insertion loss of 0.5 dB. The filter is spurious-free up to 2.72 GHz.